The invention relates to a biological electrode for detecting an electrical signal of a living body, and to a connector for use with a biological electrode (hereinafter called a “biological electrode connector”) for leading an electrical signal from the biological electrode. More particularly, the invention relates to a biological electrode and a biological electrode connector which have a superior waterproof characteristic.
An ambulatory ECG (electrocardiogram) recorder is known as a device for measuring an electrical vital-sign signal; for example, an electrocardiogram signal, over a relatively long time period. Biological electrodes are attached to the breast or the like of a subject, and an electrocardiogram signal to be measured is recorded by a portable ambulatory ECG recorder.
Since measurement and recording operations take a relatively long time period, while the ambulatory ECG recorder performs measurement, a subject has a desire for washing away, under a shower, the sweat that builds up in the course of daily life.
However, biological electrodes and biological electrode connectors of a conventional ambulatory ECG recorder have insufficient waterproof characteristics. When the subject showers, water moisture comes into contact with conductive portions of the electrodes and the connectors, thereby causing noise. For this reason, the subject is usually not allowed to shower. In order to permit the subject to shower, considerably-large waterproof seals are affixed to the biological electrodes from above, to thereby ensure the water resistance of the biological electrodes and that of the biological electrode connectors.
Affixing of such large-size seals poses limitations on a body surface to be subjected to the shower, and areas of the body surface covered with the waterproof seals become stuffy. Further, when the body is moved with the waterproof seals affixed thereon, the skin is stretched. Therefore, demand has arisen for a biological electrode and a biological electrode connector which enable a subject to shower without a necessity for affixing large waterproof seals to the body.
Biological electrodes and biological electrode connectors, both having waterproof characteristics, are disclosed in Japanese Patent Publication No. 1-48015B2. The biological electrode is formed by placing an electrode plate in a suction cup made of waterproof, elastic synthetic resin. When the suction cup is pressed from the outside, a contact sheet affixed to an internal surface of the suction cup comes into intimate contact with the body surface.
However, restoration force; that is, the force required by the suction cup to restore its original shape, is always exerted on the body surface. Hence, if the biological electrode is attached to a body surface for a long time period, there may arise a risk of inflammation of areas on the body surface where the contact sheet is to be attached. Further, the restoration force exerted on the body surface makes the subject feel uncomfortable.
Japanese Patent Publication No. 8-317913A discloses a device for measuring an electrocardiogram signal with a waterproof characteristic. A plurality of biological electrodes, a device for recording an electrical signal, and a battery are covered with a sheet-like waterproof base member in a watertight manner. An area on a body surface where the sheet-like base member is to be attached is large, and hence limitations are imposed on the body surface to be subjected to the shower, thus preventing the subject from being refreshed.
A related-art biological electrode connector is disclosed Japanese Utility Model Publication No. 2605272Y2. One side of each sheet-like conductive terminal of a biological electrode is provided with a conductive adhesive layer. A through hole is formed in an end portion of the terminal. A projecting section is provided at the extremity of a connector. The projecting section is inserted into the through hole, thereby electrically connecting the connector to the biological electrode. This configuration is superior, in that the connector is caught by the biological electrode without fail. However, a conductive portion in a connecting part between the electrode and the connector is exposed, thus failing to consider waterproofing.